Interrupts in printing with digital presses are undesired as they reduce productivity and print quality consistency. Interruptions are caused, inter alia, due to the need to check print samples of new printing jobs and/or inspections of the printing blanket or other internal sub systems. This generally requires printing a special job, such as a cleaner page or a test page and inspecting that page. It may also be necessary to print exemplars of a later print job, for inspection before starting that print job. To improve work flow it may be convenient to print such proofs during a previous print job.
In sheet fed printers the printing of a special job interleaved with the output of a long print job is not problematic, since digital presses are capable of fast switching of print content and since a sheet produced by the special job is easily removed from the output or just directed to a bypass tray. However, when the print medium is a web, then the special job must be removed from the web and the web spliced if it is desired to view the sheet out side of the press, or for keeping the output web with current job only without interruptions of special jobs. This reduces the throughput of the printer.
H-P Indigo presses generally comprise a photoreceptor sheet attached to a drum (PIP) on which an image is formed and an intermediate; transfer member (ITM) via which the image is transferred to a final substrate. Occasional cleaning of the ITM is necessary. The devices clean the ITM using a roll of plastic to which a cleaning pattern or a full coverage of the ITM is transferred to remove any particles that may have been accumulated on the ITM. Generally, for safety reasons, the printer is stopped before removing this roll of plastic from the print structure.